Acidproof, hydrolysis-resistant optical and ophathalmic glass of low density

ABSTRACT

An improved optical glass having an index of refraction of ≧1.69, an Abbe number of ≧38, and a density of ≦3.25 g/cm 3 , represents a further development of another optical glass recently provided by the same inventors. The new glass has improved suitability for continuous-tank manufacture and increased acidproofness and differs from the other glass in its content of 0.5-4.0% by weight of P 2  O 5  ; its sum total of SiO 2  +B 2  O 3  +Al 2  O 3  +P 2  O 5  being 38.5-41.5% by weight; and its sum total of MgO+CaO being 13-17.5% by weight. The full glass composition, e.g. is in % by weight: 
     
         ______________________________________                                    
 
    
            SiO 2                                                           
             26.0-32.5                                                    
       B 2  O 3                                                     
              6.0-12.0                                                    
       Al 2  O 3                                                    
               0-3.0                                                      
       P 2  O 5                                                     
             0.5-4.0                                                      
SiO 2  + B 2  O 3  + Al 2  O 3  + P 2  O 5  =        
38.5-41.5                                                                 
       Li 2  O                                                         
             0-5                                                          
       Na 2  O                                                         
             0-6                                                          
       K 2  O                                                          
             0-8                                                          
Li 2  O + Na 2  O + K 2  O = 4.5-12.0                            
       MgO   0-8                                                          
       CaO    9-16                                                        
MgO + CaO = 13-17.5                                                       
       SrO   0-6                                                          
       BaO   0-5                                                          
       ZnO   0-7                                                          
       PbO   0-4                                                          
SrO + BaO + ZnO + PbO = 0-7                                               
MgO + CaO + SrO + BaO + ZnO + PbO = 17-24                                 
       La 2  O 3                                                    
              6-11                                                        
       ZrO 2                                                           
             5-8                                                          
La 2  O 3  + ZrO 2  = 13.5-17.5                                  
       TiO 2                                                           
             5-9                                                          
       Nb 2  O 5                                                    
               6-11                                                       
       WO 3                                                            
             0-4                                                          
TiO 2  + Nb 2  O 5  + WO 3  = 14-18                           
La 2  O 3  + ZrO 2  + TiO 2  + Nb 2  O 5  + WO 3  =  
28-33                                                                     
ZrO 2  + TiO 2  + Nb 2  O 5  = 20-26                          
______________________________________

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of copending, commonly assigned application Ser. No. 282,787, filed on July 13, 1981, whose entire disclosure is incorporated by reference herein.

BACKGROUND OF THE INVENTION

Copending, commonly assigned U.S. application Ser. No. 282,787 of July 13, 1981 and its equivalent Federal Republic of Germany application No. P 30 26 605.8 describe an acidproof, hydrolytically stable, optical and ophthalmic glass of low density wherein the sum total of vitrifying agents SiO₂ +B₂ O₃ +Al₂ O₃ +GeO₂ is 25-39% by weight. It can also comprise P₂ O₅ instead of GeO₂. However, it is desired that this glass be improved for certain applications.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide optical and ophthalmic glasses of high acidproofness and hydrolysis resistance having an index of refraction n_(d) of ≧1.69, e.g., 1.69-1.71, an Abbe number (v_(d))>38, e.g., up to about 43, expansion coefficients α₂₀°-300° C. of about (80-97)·10⁻⁷ and a density (ρ)≦3.25, e.g., of 3.15-3.25 g/cm³, and which can be continuously melted in a melting tank (crucible) and subsequently can be automatically press-molded.

Upon further study of the specification and appended claims, further objects and advantages of this invention will become apparent to those skilled in the art.

These objects have been attained by the finding that the suitability of the glass of the earlier applications of continuous-tank manufacture can be still further improved by entirely omitting GeO₂, incorporating P₂ O₅ as a necessary component, and raising the sum total of vitrifying agents SiO₂ +B₂ O₃ +Al₂ O₃ +P₂ O₅ to 38.5-41.5% by weight. In addition, the glass of this invention has even further increased values of acid resistance.

Moreover, the quantitative ranges of the remaining glass ingredients in the novel glass of this invention have been considerably narrowed, in part, as compared with the quantitative ranges disclosed in the earlier applications.

DETAILED DISCUSSION

For example, borosilicate glasses are provided with 26-32.5% by weight of SiO₂ and 6-12% by weight of B₂ O₃. These, as is known, are highly resistant to hydrolysis and chemical attack.

Typical narrowed-down ranges (wt. %) for the components of the novel glasses of this invention are, e.g.,

    ______________________________________                                                SiO.sub.2                                                                            26.0-32.5                                                                B.sub.2 O.sub.3                                                                       6.0-12.0                                                                Al.sub.2 O.sub.3                                                                       0-3.0                                                                  P.sub.2 O.sub.5                                                                      0.5-4.0                                                           SiO.sub.2 + B.sub.2 O.sub.3 + Al.sub.2 O.sub.3 + P.sub.2 O.sub.5 =             38.5-41.5                                                                             Li.sub.2 O                                                                           0-5                                                                      Na.sub.2 O                                                                           0-6                                                                      K.sub.2 O                                                                            0-8                                                               Li.sub.2 O + Na.sub.2 O + K.sub.2 O = 4.5-12.0                                        MgO   0-8                                                                      CaO    9-16                                                             MgO + CaO = 13-17.5                                                                   SrO   0-6                                                                      BaO   0-5                                                                      ZnO   0-7                                                                      PbO   0-4                                                               SrO + BaO + ZnO + PbO = 0-7                                                    MgO + CaO + SrO + BaO + ZnO + PbO = 17-24                                             La.sub.2 O.sub.3                                                                      6-11                                                                    ZrO.sub.2                                                                            5-8                                                               La.sub.2 O.sub.3 + ZrO.sub.2 = 13.5-17.5                                              TiO.sub.2                                                                            5-9                                                                      Nb.sub.2 O.sub.5                                                                       6-11                                                                   WO.sub.3                                                                             0-4                                                               TiO.sub.2 + Nb.sub.2 O.sub.5 + WO.sub.3 = 14-18                                La.sub.2 O.sub.3 + ZrO.sub.2 + TiO.sub.2 + Nb.sub.2 O.sub.5 + WO.sub.3 =       28-33                                                                          ZrO.sub.2 + TiO.sub.2 + Nb.sub.2 O.sub.5 = 20-26                               ______________________________________                                    

A preferred class of glasses has the following composition (wt. %)

    ______________________________________                                         SiO.sub.2      29-32                                                           B.sub.2 O.sub.3                                                                               7.5-10                                                          P.sub.2 O.sub.5                                                                               0.5-2.5                                                         Al.sub.2 O.sub.3                                                                              0-3                                                             SiO.sub.2 + B.sub.2 O.sub.3 + Al.sub.2 O.sub.3 + P.sub.2 O.sub.5 =             38.5-41.5                                                                      Li.sub.2 O     0.5-4                                                           Na.sub.2 O     1.5-3.5                                                         K.sub.2 O      2.5-7                                                           Li.sub.2 O + Na.sub.2 O + K.sub.2 O = 6-10                                     MgO            1.0-5.0                                                         CaO            10.0-13.5                                                       MgO + CaO = 13-17                                                              SrO            0-5                                                             ZnO            0-7                                                             BaO            0-5                                                             PbO            0-4                                                             SrO + ZnO + BaO + PbO = 0-7                                                    MgO + CaO + SrO + ZnO + BaO + PbO = 16-22                                      La.sub.2 O.sub.3                                                                               6-11                                                           ZrO.sub.2      5-8                                                             La.sub.2 O.sub.3 + ZrO.sub.2                                                                  13.5-17.5                                                       TiO.sub.2      5-9                                                             Nb.sub.2 O.sub.5                                                                               6-11                                                           TiO.sub.2  + Nb.sub.2 O.sub.5 = 15-17                                          La.sub.2 O.sub.3 + ZrO.sub.2 + TiO.sub.2 + Nb.sub.2 O.sub.5 = 28-33            ZrO.sub.2 + TiO.sub.2 + Nb.sub.2 O.sub.5 21-25                                 ______________________________________                                    

The most preferred glasses have the following compositions (wt. %):

    ______________________________________                                                SiO.sub.2                                                                            30.5-31.5                                                                B.sub.2 O.sub.3                                                                      8.0-9.0                                                                  Li.sub.2 O                                                                           1.0-2.0                                                                  Na.sub.2 O                                                                           2.0-4.0                                                                  K.sub.2 O                                                                            3.0-5.0                                                                  MgO   2.0-4.0                                                                  CaO   11.0-13.0                                                                La.sub.2 O.sub.3                                                                     8.5-9.5                                                                  ZrO.sub.2                                                                            6.5-8.0                                                                  TiO.sub.2                                                                            7.0-9.0                                                                  Nb.sub.2 O.sub.5                                                                     7.0-9.0                                                                  SrO   2.0-4.0                                                                  P.sub.2 O.sub.5                                                                      1.0-2.0                                                           or                                                                                    SiO.sub.2                                                                            29.0-30.5                                                                B.sub.2 O.sub.3                                                                       8.0-10.0                                                                Li.sub.2 O                                                                           2.0-4.0                                                                  Na.sub.2 O                                                                           2.0-4.0                                                                  K.sub.2 O                                                                            3.0-5.0                                                                  MgO   3.0-5.0                                                                  CaO   10.0-12.0                                                                La.sub.2 O.sub.3                                                                     7.0-8.5                                                                  ZrO.sub.2                                                                            7.0-8.0                                                                  TiO.sub.2                                                                            6.0-8.0                                                                  Nb.sub.2 O.sub.5                                                                      9.0-11.0                                                                P.sub.2 O.sub.5                                                                      1.0-2.0                                                                  ZnO   3.0-5.0                                                           ______________________________________                                    

All details of making and using the glasses of this invention are the same as disclosed in parent applications Ser. No. 282,787 unless specified otherwise herein, or inconsistent with anything disclosed herein; e.g., the glasses of this invention will be advantageous in use because of the superior preparation discussed above. Considerations analogous to those discussed in the earlier application can be routinely and conventionally used to determine precise compositions for glasses having desired properties. For example, a portion of the oxygen content of the glass, e.g., up to 1.0 weight percent can, optionally, be replaced by F-atoms.

EXAMPLES

Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. The following preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever. In the following examples, all temperatures are set forth uncorrected in degrees Celsius; unless otherwise indicated, all parts and percentages are be weight.

The following examples illustrate typical compositions of this invention and their advantageous properties.

                  TABLE                                                            ______________________________________                                         Example      1       2         3     4                                         ______________________________________                                         SiO.sub.2    31.05   31.60     31.50 29.74                                     B.sub.2 O.sub.3                                                                             8.83    8.50      8.73  9.27                                      Li.sub.2 O   1.10    --        1.09  3.00                                      Na.sub.2 O   2.74    2.65      2.71  2.18                                      K.sub.2 O    4.15    4.00      4.10  3.30                                      MgO          2.97    4.00      1.96  4.05                                      CaO          12.39   11.30     12.25 10.43                                     La.sub.2 O.sub.3                                                                            8.93    7.65      9.49  7.37                                      ZrO.sub.2    7.56    7.30      7.47  7.74                                      TiO.sub.2    8.04    6.50      7.47  6.33                                      Nb.sub.2 O.sub.5                                                                            7.50    9.10      7.74  10.70                                     P.sub.2 O.sub.5                                                                             1.10    0.85      0.71  1.80                                      SrO          3.56    3.65      4.78  --                                        ZnO          --      2.90      --    4.09                                      nd           1.70117 1.69291   1.69821                                                                              1.70407                                   vd           39.37   39.69     39.73 39.36                                     ρ        3.20    3.22      3.23  3.19                                      AR.sup.(1)   2       2         2     2                                         CRYSTALL.5.sup.(2)                                                             OEG          /1040   /1010     /965  /975                                      Kg max/T     2.1/935 1.3/930   1.7/885                                                                              2.6/870                                   ______________________________________                                          NOTES TO TABLE                                                                 .sup.(1) Determination of resistance to acids according to the method          described in Schott Catalogue 311 d (1980) "Optisches Glass" (Optical          Glass)                                                                         .sup.(2) Carrier sheet test described in: Grauer, O. H. and Hamilton, D.       H., J. Research NBS 44,495 (1950).                                       

5=5 min tempering

OEG=upper divitrification temperature

Kg max/T-maximum crystal growth rate in μ/min/ at corresponding temperature (°C.).

The preceding examples can be repeated with similar success by substituting the generically or specifically described reactants and/or operating conditions of this invention for those used in the preceding examples. From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention, and without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions. 

What is claimed is:
 1. An optical and ophthalmic glass having n_(d) 22 1.69, v_(d)≧ 38, a density ≧3.25 g/cm³, an expansion coefficient α₂₀°-300° C. of (80-97)·10⁻⁷, a high acid and hydrolysis resistance and sufficient stability for continuous-tank manufacture,consisting essentially of, in wt. %,
 2. A glass of claim 1, of the composition in % by weight.

    ______________________________________                                         SiO.sub.2      29-32                                                           B.sub.2 O.sub.3                                                                               7.5-10                                                          P.sub.2 O.sub.5                                                                               0.5-2.5                                                         Al.sub.2 O.sub.3                                                                              0-3                                                             SiO.sub.2 + B.sub.2 O.sub.3 + Al.sub.2 O.sub.3 + P.sub.2 O.sub.5 =             38.5-41.5                                                                      Li.sub.2 O     0.5-4                                                           Na.sub.2 O     1.5-3.5                                                         K.sub.2 O      2.5-7                                                           Li.sub.2 O + Na.sub.2 O + K.sub.2 O = 6-10                                     MgO            1.0-5.0                                                         CaO            10.0-13.5                                                       MgO + CaO = 13-17                                                              SrO            0-5                                                             ZnO            0-7                                                             BaO            0-5                                                             PbO            0-4                                                             SrO + ZnO + BaO + PbO = 0-7                                                    MgO + CaO + SrO + ZnO + BaO + PbO = 16-22                                      La.sub.2 O.sub.3                                                                               6-11                                                           ZrO.sub.2      5-8                                                             La.sub.2 O.sub.3 + ZrO.sub.2                                                                  13.5-17.5                                                       TiO.sub.2      5-9                                                             Nb.sub.2 O.sub.5                                                                               6-11                                                           TiO.sub.2  + Nb.sub.2 O.sub.5 = 15-17                                          La.sub.2 O.sub.3 + ZrO.sub.2 + TiO.sub.2 + Nb.sub.2 O.sub.5 = 28-33            ZrO.sub.2 + TiO.sub.2 + Nb.sub.2 O.sub.5 21-25                                 ______________________________________                                    


3. A glass of claim 1, of the composition in % by weight,

    ______________________________________                                                SiO.sub.2                                                                            30.5-31.5                                                                B.sub.2 O.sub.3                                                                      8.0-9.0                                                                  Li.sub.2 O                                                                           1.0-2.0                                                                  Na.sub.2 O                                                                           2.0-4.0                                                                  K.sub.2 O                                                                            3.0-5.0                                                                  MgO   2.0-4.0                                                                  CaO   11.0-13.0                                                                La.sub.2 O.sub.3                                                                     8.5-9.5                                                                  ZrO.sub.2                                                                            6.5-8.0                                                                  TiO.sub.2                                                                            7.0-9.0                                                                  Nb.sub.2 O.sub.5                                                                     7.0-9.0                                                                  SrO   2.0-4.0                                                                  P.sub.2 O.sub.5                                                                      1.0-2.0                                                           ______________________________________                                    


4. A glass of claim 1, of the composition in % by weight,

    ______________________________________                                                SiO.sub.2                                                                            29.0-30.5                                                                B.sub.2 O.sub.3                                                                       8.0-10.0                                                                Li.sub.2 O                                                                           2.0-4.0                                                                  Na.sub.2 O                                                                           2.0-4.0                                                                  K.sub.2 O                                                                            3.0-5.0                                                                  MgO   3.0-5.0                                                                  CaO   10.0-12.0                                                                La.sub.2 O.sub.3                                                                     7.0-8.5                                                                  ZrO.sub.2                                                                            7.0-8.0                                                                  TiO.sub.2                                                                            6.0-8.0                                                                  Nb.sub.2 O.sub.5                                                                      9.0-11.0                                                                P.sub.2 O.sub.5                                                                      1.0-2.0                                                                  ZnO   3.0-5.0                                                           ______________________________________                                    


5. A lens made of the glass of claim 1 or
 2. 6. A lens of claim 5 wherein the lens is an eyeglass lens. 